The invention relates to the preparation and use of artificially prepared, finely divided silicic acids made by wet precipitation and which are simultaneously suitable as filtering auxiliaries and as beer stabilizers in the filtration of beer.
Finely divided silicic acids of natural origin as well as finely divided silicic acids prepared by synthetic means have long been known.
Silicic acids are used in various industries, e.g. as fillers for natural and synthetic rubber, as pigments in paints, in the manufacture of pharmaceutical and cosmetic powders, as substrates for catalysts, and as filtering auxiliaries or stabilizers in the manufacture of beer as indicated in East German Pat. No. 54 671 and in "The Use of Silica Hydrogels for Combined Filtration and Stabilisation," by Clark et al., in The Brewer, June 1980, pp. 168-171.
Users of silicic acid have varying requirements. A silicic acid with a certain set of characteristics is desirable for each special area of use, and certain characteristics of a silicic acid may be advantageous for one intended use but greatly disadvantageous for another intended use. It follows that silicic acid in one of its forms which is a good filler for elastomers cannot be assumed to be suitable in that same form as a filtering auxiliary or stabilizing agent in the manufacture of beer. Each of the known silicic acid manufacturing processes result in silicic acids which can be used advantageously in specific and limited areas of application.
In the filtration of beer, the known synthetic silicic acids made by wet precipitation and suitable as fillers exhibit a series of disadvantages. In their initial state, they are too finely divided. Their mechanical stability is inadequate, so that during filtration according to the settling process the silicic acid is broken down by metering equipment such as pumps and agitators into still finer particles, and the filter becomes clogged within a very short time.
Alternatively, the beer may be simultaneously freed of turbidity in a continuous contact process by filtration with hydrogels rather than filtering auxiliaries, and stabilized by albumin adsorption. The hydrogel, which acts as a filtering auxiliary and adsorbent, may be overburdened by adsorbed albumin and turbidity and after a short time a very high pressure difference may be noted between the filter inlet and outlet indicating filter clogging. In addition, excessive albumin adsorption adversely influences beer quality. Although a number of filter kieselguhrs and some synthetically prepared silicic acids are known as being suitable for beer filtration, there is still a need for an improved, synthetically prepared silicic acid which does not exhibit the disadvantages described above and for processes for its preparation.